Quite simple: PDVD9 will not play 1 out of a few hundred discs without AnyDVD involved. With AnyDVD active, you'll turn every one of the few thousands of discs into ANOTHER disc, effectively doubling the number of discs that potentially get presented to PDVD9, nearly doubling the number of discs that will not get played (of course factor 2 is much exaggerated - but as far as I can see, here we're looking at one out of twelvethousand discs that doesn't play).
Just a question of statistics.
In the past there were numerous discs that only played WITH AnyDVD enabled but not without.
But certainly, PDVD does try to check whether a disc has been touched by AnyDVD, so a BD-R will be a first hint.
Still, AnyDVD makes clean and conforming non-AACS Blu-Rays. I'll take a look at this specific disc sometime anyway.